PARIS – Father Jean-Marc Fournier is no stranger to fires – or danger.

Four years ago the chaplain to the Paris Fire Brigade tended to wounds and helped evacuate victims from an extremist attack at the Bataclan concert hall in Paris, where 90 people were killed.

On Monday night, Fournier, 53, who previously served in Afghanistan as a military chaplain, was at it – doing courageous things – again. He bravely entered Paris’ flame-engulfed Notre Dame cathedral to rescue priceless relics and historical treasures from the burning medieval building.

Religious artifacts Fournier and other firefighters helped save, according to accounts of witnesses confirmed by his employer and the city’s mayor’s office, were the Blessed Sacrament (used during church services to represent the body and blood of Jesus Christ) and the Crown of Thorns (purportedly worn, Catholics believe, by Jesus Christ at his crucifixion).

Paris’ public prosecutor Remy Heitz said Tuesday the cause of the fire that tore through the 850-year-old cathedral, causing its wooden roof and spire to collapse, was not yet known, although investigators are “favoring the theory of an accident” possibly linked to extensive renovation works, he said.

Heitz said it would be a “long and complex” investigation.

As for rebuilding, French President Emmanuel Macron said in a live television address Tuesday that the aim is to have it done within five years.

But if Monday night in Paris was defined by the horrific prospect of losing entirely the famous landmark, which draws an estimated 13 million visitors a year and has been the scene of numerous historic events from Napoleon Bonaparte’s coronation to the beatification of Joan of Arc, then Tuesday was about relief that an outright catastrophe was avoided.

“For hundreds of years it’s been there. It’s the story of Paris, and even the story of France,” said Michelle Massiani, 74, who has lived around the corner from Notre Dame for 45 years with her husband Claude, 77.

The Massianis linked arms as they joined a throng of residents, tourists and police who were shuffling along Paris’s packed streets Tuesday in the shadow of the cathedral’s charred tower and interior.

Many were engaged in conversations about their first encounter with a building whose importance to the French is neatly encapsulated in a plaque that sits outside Notre Dame reading: “Point Zero.” It marks the capital’s official center and also is how all distances to Paris from other parts of France are measured.

“Every day we say to ourselves ‘it can snow or it can rain, it can be day or night, we just love it. Even our granddaughter, who is 14 and quite the teenager, she is so fond of Notre Dame,” Michelle Massiani said.

Firefighters worked through the night Monday to save the cathedral. The fire was fully extinguished just after 9:30 a.m. local time (3:30 a.m. ET).

Michelle and Claude Massiani, who have lived around the corner from the Notre Dame cathedral for 45 years.(Photo: Kim Hjelmgaard / USA TODAY)

The cathedral’s imposing twin bell towers remain visibly intact, although officials said it’s too early to ascertain how structurally sound the building remains.

Olivier Latry, one of three musicians who plays the church’s 18th century organ each week that boasts 8,000 pipes, told USA TODAY that the instrument also appeared to have survived with minor damage.

“It’s very fragile. We hope it’s okay,” he said. “Before we can even consider playing it first they need to restore electricity.”

None of the organists was in the cathedral at the time of the fire.

Officials said other treasures inside the cathedral, such as a dozen large paintings of religious scenes and huge bells made famous by the bell-ringer in Victor Hugo's 1831 novel "The Hunchback of Notre Dame,” were also spared, after a plan to safeguard heritage was quickly put into action.

That plan, according to French media, involved firefighters such as Fournier forming a human chain with assistance from church employees to remove as many important items as possible. A photo taken of Fournier by KTO, a French Catholic television channel, shows him in front of the cathedral late Monday, one of among 400 firefighters who tackled the blaze for more than nine hours.

The Paris Fire Brigade said that, for the time being, Fournier was not available to be interviewed. A public profile of him on the Paris Fire Brigade’s website describes him as “difficult to miss with his small mustache and outspoken nature.”

France’s Deputy Interior Minister Laurent Nunez said efforts to save the cathedral’s stone structure and two towers “came down to 10 to 15 minutes.” Nunez said fires that started in Notre Dame Cathedral were stopped before they had an opportunity to spread and that it was only this “small window” and the heroic efforts of firefighters that staved off more damage.

Stephane Bern, a popular French television presenter of history programs who French President Emmanuel Macron has put in charge of heritage renovation programs across France, said many of the items rescued from the cathedral, including the Blessed Sacrament and Crown of Thorns, are being stored at the Lourve Museum and Paris City Hall. He said the interior of the cathedral is full of wood from the collapsed roof and water from the firefighting effort.

Bern estimated the cost of fully restoring Notre Dame to be somewhere between 1 billion ($1.13 billion) and 2 billions euros and that while some of France’s richest men, including billionaire luxury tycoons Bernard Arnault and Francois Pinault, had already pledged several hundred million dollars to that effort more needed to be done.

He pledged to present a television show to raise more funds. This will take place on Saturday on France 2, a state-funded television channel.

Donations are being pledged from everywhere, including the United States. The University of Notre Dame announced it would donate $100,000.

“We measure how much we love something once it is lost,” Bern said. “We need to rebuild and we need do it now. We need to act fast, for our identity.”